They’re designed for use with the Fathom tether, standard Cat5 cable, or even a single twisted pair of wires

Yet I am a little confused whether it would work on a non twisted pair of wires?
The kind of tether I have (not Fathom) has got 8 pins = 8 wires running inside, is not copper neither twisted. In fact it’s just for “powering” stuff.
It will not work as an ethernet cable for the above reasons, so thinking of utilizing the Fathom-X board but before I go ahead with it can I ask for some advice, whether it will work?

The Fathom-X Homeplug communication will work over any pair of conductors- twisted, untwisted, coaxial, copper, or otherwise. Homeplug was actually originally designed to work over un-shielded and untwisted household electrical wiring.

How far it will be able to communicate over that cable with usable bandwidth is another matter. The presence of twisting, shielding, as well as the impedance, capacitance, and frequency response of the cable/conductors will all affect this.

In any cable, the bandwidth will decrease as length increases, and the rate of decrease may accelerate or there may be a sudden drop in bandwidth past a certain point. This is completely dependent on the above factors and the interactions between them.

@adam Thanks for the thorough answer, I was sort of hoping that, so it’s reassuring. In the meantime I found out it’s a silver plated copper cable that runs inside (untwisted). It should work, I only really need 30m at max. I’ll go ahead and get a set as soon as it’s available.

@gcelec It will be for a special project, not strictly speaking a ROV, so won’t have ESCs and motors to introduce noise, so hopefully I’ll be fine with the untwisted tether I got